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Hi,

I need to know how to calculate the force generated on to a pitched single story extension roof by snow falling from the main house two storey roof onto it (i.e slid of the main house onto the extension roof)

The snow caused the single storey roof to fail, so i am trying to work out how much impact force was experienced, so i can defend my position.

Any help greatly appreciatted.

Cheers
 

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Pompass Ass
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hi,

i need to know how to calculate the force generated on to a pitched single story extension roof by snow falling from the main house two storey roof onto it (i.e slid of the main house onto the extension roof)

the snow caused the single storey roof to fail, so i am trying to work out how much impact force was experienced, so i can defend my position.

Any help greatly appreciatted.

Cheers

e= mc²
 

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The total sliding snow load per unit length of eave is is .4xpxW where W is the horizontal distance from the eave to the ridge for the sloped upper roof and p is the flat roof snow load which varies by location. This info is in ASCE 7-05

Bunt
 

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The roof failed because it was not maintained.

You cant just let the snow pile up there and do nothing about it and expect everything to be Ok.

You roofers up north should be doing nothing but removing snow off roofs all day, every day.
 

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Remove snow from roofs all day, every day hahahahhahahahahahahhahahahahaha.


I suppose when hurricanes strike land all you hurricane belt roofers are up there holding down the roofs too during 200 km/hr gusts...

:rolleyes:
 

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I'd say it depends on the weight of the snow that fell, light powdery snow obviously weighs les than heavy moisutr leaen snow. It also depends on the distance it fell. I think there is no real way of knowing exactly what the imapct damage was.

When you say failed, what do you mean exactly?
 

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Sean
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Remove snow from roofs all day, every day hahahahhahahahahahahhahahahahaha.


I suppose when hurricanes strike land all you hurricane belt roofers are up there holding down the roofs too during 200 km/hr gusts...

:rolleyes:
:clap::clap::clap:Brilliant, simply brilliant - pre position all the storm chasers & low ballers before the storms hit... I think we should also have some architects study the effects on the houses also during the storm - they can earn some CEU's while doing it...
 

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Remove snow from roofs all day, every day hahahahhahahahahahahhahahahahaha.


I suppose when hurricanes strike land all you hurricane belt roofers are up there holding down the roofs too during 200 km/hr gusts...

:rolleyes:
Remove snow from roofs all day, every day
I apologize. I shouldn't have said that.
I was wrong.

I was imagining that it was my roof.
I can imagine all those poor nails rusting away and in my head i can see the daily damage.
I also can see many people that cant afford to do it.
And people that dont have the physical capabilitys.
Snow has got to suck for a homeowner.
I honestly feel real sorry for anybody that has to have snow on their roof for a long period of time.
Its gotta be tough on everybody.
 

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Structural Engineer
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I do falling impact calculations a lot in my line of work. Mostly with human bodies (fall protection systems). The equivalent static force is a function of the distance the load falls from rest, the weight of the falling load, the weight of the structure itself, and the deflection you want to limit the structure to.

But if the roof failed, you basically exceed the maximum load of some member or members of the structure (could be a nail, a run of rafters, the ridge beam, etc), and pushed it beyond it's yield point.

If you're trying to defend yourself against a claim for a structural failure, call a forensic engineer. They do this for a living.
 

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The reality is that for a good portion of us northerners, snow is part of life. At times yea it does suck, but the key is to learn to deal with it. For the most part, that means shovelling as little as you possibly have to, because it isn't easy either.

I saw a thread in here about how much to charge for shovelling roofs. In this neck of the woods, it is part of the job, NOBODY gets paid for that specifically. You might get paid to fix the leak, but of course to do that you are going to have to clear the snow first., so again, it is PART OF THE JOB.

I generally don't advise clearing snow off roofs unless you have a problem. Shovels tend to be bad for shingles and most any other roofing product, let alone methods used to keep a person up there without sliding off (korkers etc)

There are ways to deal with snow and in fact where extreme snow conditions are experienced, it is better to keep the snow up there, or you won't be able to get in the door! Generally speaking in those conditions you don't see a lot of shingled roofs either ;).





As already stated, there are formulas to figure out the impact, however as also stated, it depends upon the snow type, and specifically snow load for your area. Seeing as how every snowfall varies, you have to go with whatever snowload rating is used for the area and work with that. I can guarantee you my house gets a different amount of snowflakes in any given snowfall than the neighbors, but I can also guarantee you nobody counts each individual snowflake, let alone do they install weigh scales into roofs.

In this case you are going to have to figure out the impact as well as the snow load already in place (heavy snow falling onto another pile of heavy snow). It sounds to me like it is a lot, and quite possibly this may have been an instance where you would have wanted to keep the snow on the upper roof in the first place...ie snowguards/snowfence/snowstops etc etc.



The most amusing part of roof snow removal are the people that expect you to shovel it off their sidewalk afterwards :laughing:.
 

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Here are some numbers for you

Light Dry Snow - 3.12 lbs per cu ft
Heavy Wet Snow - 20.81 lbs per cu ft
Ice - 57.25 lbs per cu ft
Water - 62.43 lbs per cu ft

Now all you have to do is figure what the weight of the snow you had, how much was on the lower roof, and how much came down on it. Then you need to know what snow load the roof was designed for.

A roof that was designed for a 25 lb snow load will hold:
96.1 inches of light dry snow
14.4 inches of heavy wet snow
5.2 inches of ice
4.8 inches of water
 

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I do falling impact calculations a lot in my line of work. Mostly with human bodies (fall protection systems). The equivalent static force is a function of the distance the load falls from rest, the weight of the falling load, the weight of the structure itself, and the deflection you want to limit the structure to.

But if the roof failed, you basically exceed the maximum load of some member or members of the structure (could be a nail, a run of rafters, the ridge beam, etc), and pushed it beyond it's yield point.

If you're trying to defend yourself against a claim for a structural failure, call a forensic engineer. They do this for a living.
That's why I asked him to define failure since it's such a broad spectrum of things. If a rafter cracked, that's not the roofers fault, period. If some ice backed inside there is some gray area in regards to who is at fault.

How can someone determine the weight of the snow that has probablya lready been metled and/or blown away?
 

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I don't see what all the bother is about.

Yes, you could go and hire a forensics engineer and simulate a near identical scenario, but so what?

Do you have General Liability Insurance?

Call them and let them worry about it and defend your position.

Unless the low level structure was built by you and it was not done to code for live and dead load performance specifications, this is a simple matter firstly of the home owners contacting their Home Owners Insurance Company for an Act Of God/Nature that occurred.

Now, if their insurance company is fighting it, then it is time for your General Liability Coverage to kick in.

Ed
 

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Curmudgeon
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Would still be nice if the OP
would come back and define
"caused the single storey roof to fail".
Elaborate on the conditions,
2' of snow? 4'?......
Guess we couldn't provide the
required magic answer and
atta boy. :whistling
Boys we have yet another dissatisfied
customer on our consciences. :sad:
 

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Would still be nice if the OP
would come back and define
"caused the single storey roof to fail".
Elaborate on the conditions,
2' of snow? 4'?......
Guess we couldn't provide the
required magic answer and
atta boy. :whistling
Boys we have yet another dissatisfied
customer on our consciences. :sad:
It was probably a HO looking to sue a contractor.
 

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powder coating mogul
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71 Posts
Never passed business math.....hehehe ;)
 
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